Problem: Simplify the following expression: $x = \dfrac{k^2 + 2k - 80}{k - 8} $
Solution: First factor the polynomial in the numerator. $ k^2 + 2k - 80 = (k - 8)(k + 10) $ So we can rewrite the expression as: $x = \dfrac{(k - 8)(k + 10)}{k - 8} $ We can divide the numerator and denominator by $(k - 8)$ on condition that $k \neq 8$ Therefore $x = k + 10; k \neq 8$